1. Field of the Invention
The present invention relates to a transportable bridge deck unit in which a framework and reinforcements for forming a deck are previously assembled, for constructing the deck on bridge girders of a road bridge, railway bridge, or other bridges constructed across river or sea, or on land.
2. Related Art
A deck made of reinforced concrete which is often used for a bridge such as a road bridge is basically produced by mounting a reinforcement assembly formed by assembling necessary reinforcements such as main reinforcements, distributing bars, and the like inside a framework, and depositing concrete within the framework.
Conventionally, a framework member is made of plywood and all operational step, from assembly of the framework to construction are carried out on the bridge girders. The operations in such an environment is not only very dangerous, but also inefficient, affected by weather, and consuming wood resources in large quantities.
Also, it is laborious for workers to regularly dispose the main and distributing bar at predetermined spatial positions, to constantly dispose the reinforcements in a state in which the main reinforcements and the like are lifted with a space from a reference surface by a constant distance, and to keep the whole shape of the reinforcements in a grille configuration, on a construction site.
Furthermore, the reinforcements are assembled by welding them or tying them with wire.
In a case of using a welding method, a defective area may be generated in both of the reinforcements to be tied together.
In a case of tying the reinforcements with wire, on the other hand, such operation is manually carried out on the construction site and thus, the positions to which the reinforcements should be arranged are easily deviated.
In addition, in order to obtain further unit earthquake resistance, sufficient coupling strength between the reinforcements can not be obtained by coupling same using welding method or wiring method, and such welding or fastening with were are inefficient.
Consequently, some constructors use a prefabricated deck in which the entire deck or a portion thereof is fabricated in a plant.
However, any producing process of the prefabricated deck is complicated in structure, and the structure is not rational because it requires extra support members and too many main members.
The prefabricated deck is accompanied by various problems regarding construction on the construction site, and cost required for construction of the prefabricated deck is higher as compared with the conventional deck.
Therefore, in order to solve the various problems accompanying the above-described deck constructed on the construction site or a prefabricated deck, a process for constructing a new type of prefabricated deck, which is a compromise process between the process for constructing the deck on the construction site and the process for prefabricating the deck, is disclosed in the Japanese Unexamined Patent Publication (KOKAI)No. 8-113917.
In that, framework to be used for a concrete framework is first formed and then a deck assembly is formed by fixing main reinforcements in a framework which will serve as a bottom plate of the deck unit for a long time, and it is transferred to the construction site and concrete is deposited into the framework.
However, because the main reinforcements are conventionally maintained in the framework using wire or grasping means in the above-described new type of process for constructing the prefabricated deck, fastened portions wire are liable to become loose at the time of transfer, for example, thereby allowing the reinforcements to move.
In the case of using the grasping means, a portion caulked by a hook of the grasping means, which is generally called a shear gripping met liable to loose and because the grasping means (a shear gripping method) per se, requires a folded portion to form the hooked portion reducing the means to support heavy weight and thus the reinforcements are deflected by load due to the considerable weight of the grasping means thereby degrading the strength, durability, and earthquake resistance of the framework.